Liquid crystal display devices (LCD's) contain liquid crystal material operatively disposed between a pair of substantially planar substrates. The facing surfaces of the substrates are typically coated with a continuous layer of a transparent conductive material which serves as an electrode. One may create optical changes in the liquid crystal material by applying a voltage to selected portions of the facing electrodes. Substrates upon which the transparent conductive material is disposed is typically a high quality glass material such as Corning 7059 Glass. However, glass substrates suffer from inherent limitations. For example, glass is relatively heavy and fragile. Accordingly, glass places significant constraints upon the manufacturing process. Moreover, since glass is relatively heavy, automated fabrication machines must be built in order to accommodate the relatively heavy weight of the glass substrates.
An additional limitation to conventional glass substrates is the need for spacer bars or rods to be disposed between the facing substrates in order to assure uniform spacing between the substrates. These rods or bars are typically added to the layer of liquid crystal material disposed between the substrates. Problems inherent in the placing of the rods and bars include obscuring of the optical changes effected by the liquid crystal material. Further, the rods and bars can deleteriously effect the layer of conductive material. Moreover, there is no uniform way to disperse rods and bars in the liquid crystal material, resulting in localized heavy and light concentrations of rods and bars. Accordingly, it is difficult to assure uniform spacing between the substrates.
Recent activity has aimed at fabricating LCD's with plastic substrates. Plastic substrates are attractive as they are thinner, lighter and less susceptible to breakage than their glass counterparts. Moreover, plastic substrates lend themselves more readily to manufacturing processes. As a result, plastic substrates may also lead to higher quality, low cost displays which are more readily adaptable to different applications.
In the context of LCD's having touch-sensitive assemblies fixed thereto, heretofore it has been the practice to affix the touch sensitive panel to the front panel of the liquid crystal display. More typically, the LCD and the touch sensitive panel have been two discreet devices which have been laminated one on top of the other. As displays have heretofore been manufactured with rigid glass substrates, the touch sensitive panel is laminated on the surface of the LCD disposed closer to the viewer. This of course raises several problems. For example, the touch sensitive screen must be substantially transparent so to not adversely impact the brightness and contrast of the underlying display. Transparency depends both upon the inherent transparency of the touch panel as well as on the method by which the panel is mounted or bonded on to the display. As LCD's were typically manufactured of glass substrates, the touch panel could not be mounted on the bottom as glass is substantially rigid and will not deform under applied pressure.
Accordingly, there exists a need for a liquid crystal display device which uses lightweight flexible substrates, and which is readily integrated into a touch sensitive system. Such a device should be preferably made of a material which eliminates the need for spacer rods or bars, and which lends flexibility to the overall device structure.